added volunteer talks m2m table
added volunteer talks m2m table

cateee/fosdem-volunteers,jrial/fosdem-volunteers,jrial/fosdem-volunteers,jrial/fosdem-volunteers,jrial/fosdem-volunteers,FOSDEM/volunteers,cateee/fosdem-volunteers,FOSDEM/volunteers,cateee/fosdem-volunteers,FOSDEM/volunteers,cateee/fosdem-volunteers,FOSDEM/volunteers